Modern computers employ various forms of storage systems for storing programs and data. For example, various forms of disc drive systems have been designed to operate under the control of a computer to record information and/or retrieve recorded information on one or more recording discs. Such disc drives include hard disc drives which employ recording discs that have magnetizable (hard) recording material, optical disc drives which employ recording discs that have optically readable recording material, magneto-optical (MO) disc drives which employ recording discs that have optically readable magnetizable recording material, or the like.
Conventional disc drive systems typically include one or more recording discs supported for relatively high speed rotation on a rotary spindle. For example, FIG. 1 shows a side view of portions of a conventional disc drive system, including a conventional data storage or recording disc 200 supported on a spindle 210. A disc drive motor (not shown) is operatively coupled to the spindle 210 for rotation of the spindle and the disc supported thereon. A recording and/or reading head 220 is supported by suitable head support structure (not shown) adjacent the recording surface of the disc. To simplify the disclosure, FIG. 1 is shown with a single recording disc 200 having a single recording surface and a single head 220. However, other conventional disc drive systems employ multiple discs, double-sided discs (discs with recording surfaces on both surfaces) and multiple heads.
As shown in FIG. 1, the disc 200 has a central hub opening through which the spindle 210 extends. The disc 200 and spindle 210 are shown in a top view in FIG. 2. The spindle 210 extends through a central opening, which defines an inside diameter, of the disc. The disc is secured at its inner diameter (ID), in a fixed relation with the spindle 210, and is supported such that the outer diameter (OD) portion of the disc is free from contact with other components. In this regard, the disc is clamped at its ID to the spindle 210 and is free at its OD. When the spindle 210 is rotatably driven, the disc 200 is caused to rotate with the spindle 210. A top (not shown) which provides a protective cover for the disc is attached through the top of the spindle 210 and provides support for the spindle 210.
Typically, multiple center-open discs and spacer rings are alternately stacked on a spindle motor hub. The hub, defining the core of the stack, serves to align the discs and spacer rings around a common axis. Collectively the discs, spacer rings and spindle motor hub define a disc pack assembly.
The surfaces of the stacked discs are accessed by the read/write heads which are mounted on a complementary stack of actuator arms which form a part of an actuator assembly. Generally, the actuator assembly has an actuator body that pivots about a pivot mechanism disposed in a medial portion thereof. A motor selectively positions a proximal end of the actuator body. This positioning of the proximal end in cooperation with the pivot mechanism causes a distal end of the actuator body, which supports the read/write heads, to move radially across the recording surfaces of the discs, such that the head may be selectively positioned adjacent any recording location on the recording surface as the disc is rotated.
In operation, the head 220 is moved in the radial direction to align or register with a desired track location on the recording surface of the disc. Once aligned or registered with the desired track location, the head 220 is operated to read or write information onto the recording surface at the desired track location. It is important to properly register the head 220 with the track location to effect accurate reading or writing operations on the registered track.
Modern advances in disc drive technology have resulted in increased disc storage density and decreased track widths, such that greater amounts of information may be stored per given recording surface area. However, as track widths decrease (and storage density increases), the need for accurate head registration increases. In general, smaller track widths require greater head-to-track registration accuracies and have smaller alignment error tolerances. For example, for a disc with 393.7 tracks per cm (10,000 tracks per inch), the track width is only about 2540 .mu.mm (100 .mu.in) and the total allowable (tolerable) off-track mis-registration may be no more than about 254 .mu.mm (10 .mu.in) peak-to-peak.
Track mis-registration (TMR) may result from a variety of sources, including, for example, ball bearing non-repeatable run out, spindle-disc rocking vibrations and disc flutter. To reduce the asynchronous vibrations caused by ball bearing non-repeatable run out and spindle-disc rocking vibration, hydrodynamic motors have replaced the ball bearing motors previously used.
Although the introduction of the hydrodynamic motors reduced some vibration problems, it introduced other concerns. For instance, unlike ball-bearing motors, the hydrodynamic motors are not attached to the top cover by the central spindle. As such, the motor is susceptible to gyration due to uneven weight distribution introduced by the disc stack. Typically, the discs are stacked onto the hub in a linear manner from a specified zero location or predetermined start location, which does not change for different disc stack sizes. Thus, for instance, each disc stack might begin near the base of the hub, or the top of the hub. Each disc is stacked equidistant from each other. Thus, depending upon the number of discs, the height of discs along the hub will vary. As such, the weight distribution from the discs will vary depending upon the number of discs. However, most of the weight will be concentrated near the base or top of the hub, depending upon the zero location.
Further, depopping, which is the removal of one disc from the disc pack at a time, removes the discs from one end of the stack to the zero location. Thus, discs are removed, or depopped, from the top to the bottom or the bottom to the top of the hub.
This manner of depopping the discs enhances the uneven weight distribution. In a system utilizing a hydrodynamic motor, the uneven weight distribution causes the spindle, which is encased in a lubricating fluid, such as oil, to rise and fall and increases the likelihood that the spindle will hit the interior of the hub. The metal to metal contact can cause metal to be deposited into the oil. Due to the minute spacing between the spindle and the hub interior, the metal deposits can inhibit the spinning of the hub and cause the motor to freeze. Thus, there is a need in the industry for a method of arranging, storing and removing discs from a disc drive that does not increase the gyration of the motor.